Glass chromatography beads

Figure 2.5 Solid Phase DNA Synthesis Cycle (Contd.). Most frequently used base protecting groups are shown Bz Af-6 benzoyl (adenine), W-4 benzoyl (cytosine) N-2 isobutyroyl (guanine). All are base sensitive. DNA chain is built up from 3 to 5 on controlled-pore glass (CPG) bead solid support. Post global deprotection and resin removal, the desired product oligo-/polydeoxynucleotide is then separated initially by precipitation by means of an agent such as ethanol and purified finally by reversed phase liquid chromatography, or ion exchange chromatography as appropriate (see later in Chapter 2).

Principally two classes of material are available for exclusion chromatography either, semi-rigid cross-linked macromolecular polymers or rigid inert porous silicas or glasses—the bead size of both is in the range 5-10 pm. 

Hydrolytic Kinetic Resolution (HKR) of epichlorohydrin. The HKR reaction was performed by the standard procedure as reported by us earlier (17, 22). After the completion of the HKR reaction, all of the reaction products were removed by evacuation (epoxide was removed at room temperature ( 300 K) and diol was removed at a temperature of 323-329 K). The recovered catalyst was then recycled up to three times in the HKR reaction. For flow experiments, a mixture of racemic epichlorohydrin (600 mmol), water (0.7 eq., 7.56 ml) and chlorobenzene (7.2 ml) in isopropyl alcohol (600 mmol) as the co-solvent was pumped across a 12 cm long stainless steel fixed bed reactor containing SBA-15 Co-OAc salen catalyst (B) bed ( 297 mg) via syringe pump at a flow rate of 35 p,l/min. Approximately 10 cm of the reactor inlet was filled with glass beads and a 2 pm stainless steel frit was installed at the outlet of the reactor. Reaction products were analyzed by gas chromatography using ChiralDex GTA capillary column and an FID detector. 

Figure 8 Separation of isomeric acids (maleic and fumaric acid) by controlled surface porosity anion exchange chromatography. Column Sulfonated fluoropolymer coated onto a 50-p glass bead. Average pore size about 1000 A. Flow rate 2.73 ml/min. Eluant 10 mM HN03. Temperature 60°C. Detection absorbance. (Reproduced from Kirkland, J. J., J. Chromatogr. Sci., 7,361,1969. By permission of Preston Publications, A Division of Preston Industries, Inc.)...

Boylan and Tripp [76] determined hydrocarbons in seawater extracts of crude oil and crude oil fractions. Samples of polluted seawater and the aqueous phases of simulated samples (prepared by agitation of oil-kerosene mixtures and unpolluted seawater to various degrees) were extracted with pentane. Each extract was subjected to gas chromatography on a column (8 ft x 0.06 in) packed with 0.2% of Apiezon L on glass beads (80-100 mesh) and temperatures programmed from 60 °C to 220 °C at 4°C per minute. The components were identified by means of ultraviolet and mass spectra. Polar aromatic compounds in the samples were extracted with methanol-dichlorome-thane (1 3). 

A similar result is accomplished by using as one phase a solid powder or fine "beads" packed in a vertical column or spread in a thin layer on a plate of glass. The methods are usually referred to as chromatography, a term proposed by Tswett to describe separation of materials by color. In 1903 Tswett passed solutions of plant leaf pigments (chlorophylls and carotenes) in nonpolar solvents such as hexane through columns of alumina and of various other adsorbents and observed separation of colored bands which moved down the column as more solvent was passed through. Individual... 

Sephadex G-50 has been prepared for your use. The dry beads have been preswollen in water for several hours, fine particles that may slow column flow have been removed, and the gel has been equilibrated in Tris buffer. If chromatography columns are not available, one can easily be constructed from a glass tube (2.5 X 40 cm), cork stoppers, Tygon tubing, a screw clamp, and small glass tubing as shown in Figure E4.4. With the screw clamp closed, add 10 to 15 mL of Tris buffer and insert a small piece of... 

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